Supporting End-to-End Intelligence in Metro WDM Networks · PDF fileSupporting End-to-End...

© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 1

Supporting End-to-End Intelligence in Metro WDM Networks

David Bianchi


Major takeaway

A bit of HistoryThe WDM topology evolution

Which problem we need to solveAs WDM topology evolves, E2E intelligence becomes more and more important

What it is needed to give E2E intelligence to a DWDM network

The “bricks” of the WDM intelligence


A bit of history of DWDM “E2E”

At the beginning it was point to point

Maybe used to mimic a ring

With PtoP, intelligence was a nice to have. Intelligence still in client networks

The WDM used as fibre saving system, just a big pipe carrying wavelengths


A bit of history of DWDM “E2E”

Then real ring The ROADM revolution

And finally the all-optical mesh!

With ROADM introduction

intelligence in WDM becomes a must have


From old Network architecture Transponders manually patched

CoreClient

Metro Network

PtoP DWDM

Transponders converting short reach to λMetro

Network

Manual patching of connections


To still old Network architecturesUse cross-connects to manage bandwidth

CoreClient

Electrical XC

Metro Network

PtoP DWDM

Electrical switching – OEO conversions

Metro Network

Manual addition of WDM I/F on XC


To the new Network architecture

Metro Network

Metro Network

Alien wavelength

Photonic switching –no OEO conversions

Agile DWDM layer w/ photonic switches

CoreClient


Which problem we are going to solve ?

Wavelength can take different routes

Failures impairment on downstream added wavelength

Network topology is now complex

ITU interfaces are going anywhere

Fault management and troubleshooting becomes more and more cumbersome


The E2E intelligence bricks

Network topology discovery

Network Inherent Monitoring

Traffic survivability

Network Traffic provisioning

Better fault managementAlien Wavelength

Alarm correlation

Any serviceWavelength on the flyRobust DWDM architectureAll optical management basisNo EMS initialization


E2E Intelligence


Network Topology DiscoveryFor IP-centric folks:

In a transport network, management traffic is strictly separated from data traffic, usually in the signal OH

For TDM FolksIn a DWDM network this is even worse. There is no Signal Overhead.

OSC (additional wavelength) is usually adopted to carry management traffic

The basic step for supporting End to End intelligence is the auto-discovery of node and links

OSC


Inherent monitoringWhen a wavelength enters the DWDM network it has to be monitored end to end.WDM is analogical by nature

No BER / Packer statistics are available

This basic requirements imposes monitoring points along the path:

Photo-detectors – To monitor and report the optical powerControlled optical attenuators – To control the transmitting power budget

Monitoring points cost


Inherent monitoring – flat view

Network Monitoring is the 2nd step in the E2E intelligence

Wavelengthingress

Back to back N-degree Network junction

Intermediateamplifier

Wavelengthegress

Rx Power

Total TxPower

Total Rx Power

Span Loss monitoring

Wavelength intermediate monitoring


Network Monitoringif you have Transponder …

With transponders as demarcation point, E2E monitoring is easierBut is not enough !

End 2 End client monitoring

OTN BIP-8

FEC

G.709 trunk monitoringG.709 trunk monitoring

SONET/SDH B1/B2

OTN BIP-8

GE/10GE RMON

SAN Protocols

Client Trunk


The whole modelClientG.709 OHFEC CodingOptical Trunk

Optical Channel Port

SONET/SDH/RMONOTN BIP-8 (Section and Path)

FEC Decoder data

Per channel Optical PM (OPR, OPT)

OMS

OTS OTS OTS

ClientG.709 OHFEC CodingOptical Trunk

Optical Channel Port

OMS

OTS

Aggregate Optical PM (OPR, OPT)

Optical PM (OPR, OPT)

WDM start here


Traffic survivability


Wavelength Survivability

When a failure occurs, not only the wavelength added before the failure are affected, but also the ones added after it, can have issues

The amplification system must take into account and re-adjust the total power accordingly

Aside of protection /restoration technologies, WDM is peculiar …

This wavelength should survive


But also slow events occur ….

Fiber AgingLaser and component degradation

Environmental condition change (e.g thermal excursion)

All of the above may result in system impairments along the life.

Typically requiring the so called “truck rolls”expensive field operations to re-tune the network


E2E intelligent system has to play with both the situation

Fast, dramatic eventsFiber cut, amplifier breakout

Slow, lifecycle phenomenaAgeing (fiber, components),Environmental condition changes

Automatic Power Control is the third step on the E2E intelligence


Traffic provisioning


Wavelength provisioning

Hide complexity of WDM connection setup in point sand click operationRegardless the payload

Router

Transponder Regen (if needed)

Router

Non-IPNon-IP


Wavelength provisioning

To setup a wavelength from A to ZThere are multiple possible route in a mesh networkNetwork provisioning becomes a must to select which route has to be activated

AZ

Wavelength provisioning is the 4th component in E2E intelligence


Traffic provisioning


Alien WavelengthBy alien wavelength we mean the ability of a WDM network to carry out Wavelength coming from external devices w/o a Transponder in between

Inherent monitoring, wavelength provisioning, system robustness, are all table stake to alien wavelength support

WDMCloudWDMCloud


Alien Wavelength

With alien wavelength WDM really becomes a “cloud”,

Alien wavelength support is the fifth brick of the E2E intelligence

Support for alien wavelength means inherent monitoring, system robustness, End to end management

Intermediate monitoring becomes a must


Alarm correlation


Node level alarm correlation

A Failure at OTS Sink point has to suppress alarm on upstream layersIt means that WDM De-multiplexer and Transponder do not have to issue any alarm

OTSOMSOCH Trail OCH NC

alarm

This is easy and it is not enoughYou still have too many alarms from the network


DWDM Fault Management: a nightmare ?

DCN

Transponder 1

Transponder n

Transponder 1

Transponder n

Alarm storm

Alarm storm & DCN

Congestion

Alarm storm & DCN

Congestion

Network Map all red iconsAlarm list flooded

“Christmas Tree” effect

Alarm storm

What happen at NOC upon a fiber cut ?A real mess


The ideal situation

DCN

Transponder 1

Transponder n

Transponder 1

Transponder n

1 Alarm1 Alarm

Network Map 2 red icons

2 Alarms

What happen at NOC upon a fiber cut ?2 Alarms only!


Network Level Alarm Correlation (NLAC)

R-OADM

R-OADMR-OADM

R-OADMR-OADM

R-OADM

TRANSPONDERS

TRANSPONDERS

G.798 OTS/OMS PMI

Case 1

Dramatic failure: Fiber cut on OTS line or amplifier outage


Network Level Alarm Correlation (NLAC)

R-OADM

R-OADMR-OADM

R-OADMR-OADM

R-OADM

TRANSPONDERS

TRANSPONDERS

G.798 OCH FDI

Case 2

One channel failure: Fiber cut on patch-cord or Transponder outage

Wavelength provisioning is the last (but not least) component in E2E intelligence


Alarm Correlation in DWDM world

ITU-T G.798 drives the standard

From Optical Transport Section layer (down to the fiber)

To Optical channel layer (where the wavelength starts)

However implementation is not forced to particular techniques


Finally


Does this apply to metro networks only ?

• Long Haul is typically still at the PtoP topology approach

• O-E-O Conversion still required to support regenerators

• Add and Drop in large POPs

• Metro DWDM became the convergence layer

thanks to the ROADM technology

Less need for regeneration

Add and drop in any node


Q and A

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